Air filter alarm



Se t. 4, 1962 D. B. LEWIS AIR FILTER ALARM Filed July 21, 1958 .jilmluiii INVENTOR. 270724212? 3 fizz/2's ATTORNEY United 3,052,207 AER FELTER ALARM Donald B. Lewis, Lapeer, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed July 21, 1058, Ser. No. 749,919 1 Claim. (or. 116-117) This invention relates to alarm devices indicating when operations should be performed, and has particular relation to an alarm device that will indicate when a replaceable air filter in the air cleaner in the induction system of an engine, should be changed.

It is proposed to provide an alarm device which will indicate to the operator of an engine, such as an internal combustion engine employed in a motor vehicle, that the filter for the air cleaner should be changed. The alarm device may be a visual or other well known alarm device that the operator may sense while driving the vehicle and without being able to see or perhaps even hear the engine in operation.

In the drawing:

The single FIGURE illustrates in cross-section an induction system for an engine with an air cleaner attached and showing schematically an alarm device capable of operation when the filter device becomes sufficiently filled with dirt to require cleaning.

An induction system for supplying fuel and air for operating an internal combustion or other suitable engine embraces a throttle valve 11 controlling the flow of fuel from a suitable and well known float chamber 12 through a passage 13 leading to the throat of a venturi 14 in the induction passage 16 embraced in the induction system 10. A choke 17 may be employed in the manifold induction passage anterior to the venturi 14 for utilization in starting the engine. Beyond the choke is any suitable air cleaner 1% comprising a support 19 having an outlet 21 connected to the induction passage 16 and a cover removably secured to the support 19 by a bolt 22 and wing nut 23. A replaceable fibrous or other suitable filter 24 is secured between the support 19 and cover 20 by operation of the wing nut 23.

As the air flows into the induction system through the filter 24, the filter will collect dirt and other foreign matter which will tend to clog the filter and to decrease the flow of air through the filter at any given difference in pressure. If the filter becomes sulficiently clogged with dirt, this will decrease the fluid pressure in the passage 16 and reduce the power developed by the engine. It is therefore desirable to change the filter under such circumstances.

In order to indicate when the filter should be changed, it is proposed to provide electrical switches 26 and 27 Wired in series with an indicator 28 between the opposite stares arena Fa -rented Sept, 4, 19%2 i he poles of a battery 29. The switch 26 is a normally open switch set to close the contacts 31 at a predetermined pressure in the manifold induction passage 16. The switch 26 is pressure actuated and connected by a conduit 33 to the passage 16 between the choke 17 and the venturi 14.

Switch contacts 34 of switch 27 will be closed when air flow in passage 16 is less than a predetermined value, and open when air flow is in excess of that value. The switch 27 is actuated by the difference in pressure between the throat of the venturi and a place in the passage 16 beyond the venturi 14. The switch is connected to be actuated by the pressure in conduits indicated at 36 and 37.

The switch 26 is set to close the contacts 31 if a restriction of 2 inches of water is caused by dirt clogging the filter 24. The switch 27 is set to open the contacts 34- in the event the flow of air in the manifold induction passage 16 exceeds cubic feet per minute. These and other values may be selected at will to provide overlapping ranges for the switches 26 and 27 so that the contacts 31 and 34- both may be closed under conditions of operation of the engine when the filter 24 may cause an undesirable resistance to the flow of air to the engine.

If it were not for these overlapping ranges it might be possible for one switch to cause actuation of the alarm 2% to indicate that the filter 24 should be changed, when as a matter of fact nothing had caused the excessive depression in the induction system passage other than an excessively high speed of operation of the engine.

'I claim:

An alarm device for an air induction conduit of an internal combustion engine, said conduit comprising first and second portions of uniform diameter and an intermediate portion having a venturi throat, a pressure-responsive switch operatively connected to the first of said portions of uniform diameter, and a difierentially operated switch operatively connected to said second portion of uniform diameter and to said throat portion, said switches being in series in an electric circuit having a signal therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,618,190 Rowe Nov. 18, 1952 2,681,585 Hanert June 22, 1954 2,700,362 Calling Jan. 25, 1955 2,729,339 McCoy Jan. 3, 1956 2,843,077 Leefer July 15, 1958 2,935,040 Steensen May 3, 1960 FOREIGN PATENTS 1,083,459 France June 30, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,052,207 1962 September 4,

Donald" B.- Lewis It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 27," for "cleaning" read changing Signed and sealed this8th day of January 1963.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

